Problem: 3 crayons cost $5.37. Which equation would help determine the cost of 5 crayons?
There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 3 crayons. We want to know the cost of 5 crayons. We can write the numbers of crayons as a proportion: $\dfrac{3}{5}$ We know 3 crayons costs $5.37. We can let $x$ represent the unknown cost of 5 crayons. The proportion of these costs can be expressed as: $\dfrac{\$5.37}{x}$ The cost changes along with the number of crayons purchased, and so the two proportions are equivalent. $\dfrac{3}{5} = \dfrac{\$5.37}{x}$